The invention relates in general to press tooling components and in particular to tooling components that are combinations of steel and polyurethane.
Compaction press tooling is sometimes damaged under normal operating conditions, for a variety of reasons. Compaction tooling may be particularly hazardous when high explosive (HE) powders are used in a consolidation process. Exacting tool design, installation, and alignment contribute to the prevention of inadvertent tool damage, but conditions can arise that cause eventual damage to the system. Methods of predicting and controlling the dynamic conditions (friction, thermal, fill distribution, punch velocity, and more) that lead to such events have merit for most press systems, but additional techniques are needed for HE press tooling configurations.
Tool impingement caused by radial forces that develop in the compaction zone is difficult to control. The punch cuts into the die at the point of contact, plowing a metal chip along the wall and eventually driving it into the consolidated billet. Or worse, the metal chip is forced into the punch-die clearance, galling both tools and forcing the sharp edge to impinge upon the opposite side of the die wall. The risk of damage caused by the sharp punch edge can be mitigated by a machined round with a minimal radius of 0.005 inch. However, the machined round will allow excessive flashing to extrude into the clearance zone. Excessive flash material can be hazardous under certain conditions, and leads to a process breakdown and poor quality billets.
Typically, 0.005 inch diametric clearances are required to approach optimal press performance and product quality. Closing the clearances further improves performance and quality, but tighter tooling clearances are inherently problematic. Press-equipment design tolerances generally stack up to a greater degree, allowing encroachment of the essentially free-floating press tools. Even a simple single-action punch and die press system is subject to tooling misalignment due to these tight clearances. Dual-action presses with long ram stroke are more susceptible to hazards such as scoring and galling due to the increased tool travel through the clearance zones. Increasing the clearances may prevent tool impingement and reduce associated hazards, but increased clearances create excessive flash conditions, as described previously. A solution that maintains the tight clearances needed for performance and quality, while increasing the clearances that are causal in tooling damage, is needed.